Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus for processing aperiodic channel state information (CSI) in a wireless communication system.
Related Art
The 3GPP LTE is a technology for enabling high-speed packet communications. Many schemes have been proposed for the LTE objective including those that aim to reduce user and provider costs, improve service quality, and expand and improve coverage and system capacity. The 3GPP LTE requires reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure, an open interface, and adequate power consumption of a terminal as an upper-level requirement.
Small cells using low power nodes are considered promising to cope with mobile traffic explosion, especially for hotspot deployments in indoor and outdoor scenarios. A low-power node generally means a node whose transmission power is lower than macro node and base station (BS) classes, for example pico and femto evolved NodeB (eNB) are both applicable. Small cell enhancements for evolved UMTS terrestrial radio access (E-UTRA) and evolved UMTS terrestrial radio access network (E-UTRAN) will focus on additional functionalities for enhanced performance in hotspot areas for indoor and outdoor using low power nodes.
One of potential solutions for small cell enhancement, dual connectivity has been discussed. Dual connectivity is used to refer to operation where a given user equipment (UE) consumes radio resources provided by at least two different network points connected with non-ideal backhaul. Furthermore, each eNB involved in dual connectivity for a UE may assume different roles. Those roles do not necessarily depend on the eNB's power class and can vary among UEs.
The UE may report channel state information (CSI) to the network. For downlink (DL) coordinated multi-point (CoMP), multiple transmission points are coordinated in their DL data transmission. The UE may be configured to measure and report the CSI of a set of non-zero power CSI reference signal (RS) resources. The UE may also be configured with one or more interference measurements. Each interference measurement is associated with one CSI-interference measurement (CSI-IM) resource, which is a set of REs on which the UE measures interference. The UE may also be configured with multiple CSI processes. Each CSI process defines the CSI measurement associated with one non-zero power CSI-RS resource and one CSI-IM resource. For UL CoMP, multiple reception points are coordinated in their uplink data reception.
When dual connectivity is configured, how to process CSI efficiently may be required.